The invention relates to apparatus for the temporary storage and measured feeding of the volatile fuel components in the free space of a fuel tank system into the intake tube of an internal combustion engine. The apparatus includes a vent line connecting the free space to the atmosphere. In this vent line there is disposed a storage chamber with an absorption element, as well as a line which connects the storage chamber to the intake tube. This line can be shut by an electromagnetic check valve which has a control chamber of enlarged cross section between the check valve and the intake tube as well as an auxiliary means disposed in the control chamber for varying the opening of the check valve.
Apparatus of this type is disclosed in the German patent publication No. 35 19 292. This apparatus prevents the escape into the atmosphere of the volatile fuel components always present in the free space of the fuel tank of an internal combustion engine, and makes use of a special vent line disposed between the free space and the atmosphere which incorporates a storage chamber with an absorption element. This absorbtion element usually consists of a permeable body of active carbon that is capable of momentarily storing a considerable volume of volatile fuel. To regenerate the absorption element, fresh air is aspirated through the internal combustion engine during its normal operation, making use of a line which connects the storage chamber to the intake tube of the engine. It is to be noted, however, that at low engine running speeds and/or in the case of an especially high degree of saturation of the absorption element, the fuel-air mixture aspirated by the internal combustion engine can become "over-rich" resulting in disturbances in engine operation. The line can therefore be shut by an electromagnetic check valve through which the flow is variably controlled by means of external sensors, on the one hand, and by the vacuum in the line acting on its valve body, on the other hand.